1. Field of the Invention
The present invention generally relates to a hardcopy apparatus, such as copiers, printers, scanners, and facsimiles, and more particularly to improved media outputting devices for such apparatus.
2. Description of the Prior Art
In a hardcopy apparatus and particularly in apparatus handling media of big size, such as large format printers, printed media is outputted from the printer by means of outputting devices that may damage the quality of the printout. Conventional outputting devices, in order to advance the printed media, employ elements for holding the media having direct contact with the printed surface. This may cause markings on the media, ink smearing and other adverse affects on the print appearance.
As an example, the prior art has employed star wheel overdrives for outputting printed media. These devices may damage the printout with star wheel marks and further require the need to employ a mechanism or a structure to hold the star wheels.
To overcome the problem of adverse affects on the print media appearance, U.S. Pat. No. 6,234,472 discloses a media holddown device comprising a vacuum holddown output unit for holding at least a portion of the media down onto a surface of the outputting mechanism. Thus, Patent ""472 allows holding of the print media without direct contact with the printed surface. The vacuum holddown output unit includes a platen having a continuous waved slot that allows for even distribution of the vacuum along the print zone and a plurality of overdrive wheels with a gap between the overdrive wheels and the surrounding platen, in which a vacuum is also generated. Patent ""472 requires a vacuum that holds the print media tightly against the platen and also against the overdrive wheels. However, this vacuum undesirably increases the friction force on the platen, resulting in a lower traction force for the overdrive wheels. It also requires an increased vacuum level that is primarily used for holding the print media against the platen.
The present invention has the advantage of providing an improved media outputting device and method for outputting a printed media from a hardcopy apparatus, with an increased traction force. The present invention has the further advantages of requiring lower vacuum levels and providing a more accurate paper advance due to less friction force on the platen which does not have a vacuum distribution on
A media outputting device comprising: a media source; at least one roller having an outer surface with a contact region for engaging media where the roller is rotatable for outputting the media; and a negative pressure mechanism which is capable of creating a negative pressure distribution on the contact region wherein at least one portion of the contact region that is farther from the media source has a greater negative pressure than at least one portion of the contact region that is closer to the media source.
Preferably, the negative pressure distribution is created by a first and a second vacuum channel, the first channel running axially along the edge of the contact region closest to the media source and the second channel running along the opposite edge of the contact region wherein the width of the second channel is greater than the width of the first channel. More preferably, the negative pressure distribution is a linear distribution.
The present invention will be described further, by way of example only, with reference to an embodiment thereof as illustrated in the accompanying drawings.